Silver halide photographic processing using formazans

ABSTRACT

This application describes a process of color development of color photographic material wherein at least one silver halide emulsion layer containing a developable silver salt is color developed to yield a dye image, the developed silver and the residual silver halide being removed, the step of developing the photographic material with a color developing solution in the presence of an image-forming color coupler and a formazan compound of the formula:   WHEREIN R1 and R2 are each selected from hydrogen atoms or solubilising groups and R3 is a hydrogen atom or an aryl, alkyl, aralkyl or a -CN group or a solubilising group selected from COOH, -CH2SO3H or -CH2COOH, at least one of R1, R2 or R3 being a solubilising group, the two phenyl groups optionally carrying further substituents.

United States Patent Macdonald I 51 Feb. 29, 1972 [541 SILVER HALIDE PHOTOGRAPHIC PROCESSING USING FORMAZANS [211 Appl. No.: 793,553

[30] Foreign Application Priority Data Jan. 26, 1968 Great Britain ..4,303/68 [52] US. Cl...... .....96/55, 96/22 [51] Int. Cl v ..G03c 7/00 [58] FieldotSearch ..96/9, 55,565

[56] References Cited UNITED STATES PATENTS 3,168,400 2/1965 Blackmer et a] ..96/22 3,467,520 9/ 1969 Puschel et al. ....96l9 3,503,741 3/1970 Wilson et al ..96l99 Primary ExaminerJ. Travis Brown Att0rneyCushman, Darby & Cushman [57] ABSTRACT This application describes a process of color development of color photographic material wherein at least one silver halide emulsion layer containing a developable silver salt is color developed to yield a dye image, the developed silver and the residual silver halide being removed, the step of developing the photographic material with a color developing solution in the presence of an image-forming color coupler and a forcompound of the formula:

wherein R and R are each selected from hydrogen atoms or solubilising groups and R is a hydrogen atom or an aryl, alkyl, aralkyl or :1 CN group or a solubilising group selected from COOH, CH SO H or CH COOH, at least one of R R or R being a solubilising group, the two lbw 519925 QBEPFQRUPEXUPE er ile u t lqem I 7 Claims, No Drawings SILVER HALIDE PHOTOGRAPHIC PROCESSING USING F ORMAZANS This invention relates to color development processes for the production of color images in photographic material.

One of the difficulties associated with the processing of color photographic material which contains substantive color couplers has been to balance correctly the amount of silver halide compared to color coupler in each layer off normal tripack material. If theoretically the correct amount of color coupler is present to combine with all the oxidized color developer which would be formed if all the silver halide were reduced, a resultant dye image would be formed of too high a contrast as a dye image has pro rata a much higher covering power than a silver image. If however the amount of silver is lowered to such an amount that an acceptable resultant dye image could be expected, a very grainy image often results with a resultant lessening in the sharpness and definition of the image. One method of overcoming this difficulty has been to employ, with the substantive color coupler, a so-called competing color coupler.

When photographic material containing in each emulsion layer a relatively large amount of silver halide and a substantive coupler is exposed and developed in the presence of such a competing coupler which may be added to the emulsion layer but more usually to the developer, the oxidized color developing agent combines with both couplers. The competing coupler yields a dye which is nonsubstantive and water soluble and is removed from the film in the developer solution and subsequent washing steps. The substantive coupler yields a substantive dye image of the density required but being derived from a greater number of silver halide grains shows an improved graininess compared to images obtained from material wherein less silver halide is present initially.

Similar difficulties have been encountered when the color couplers are not present in the photographic material but are present in the color developer solution. However, competing color couplers have been successfully used in such nonsubstantive color developer processes, both the color coupler and competing color coupler being present in the color developing solution.

It is the object of the present invention to provide a color development process wherein part of the oxidized color developer is removed from the system without forming an image dye.

According to the present invention in a process of color development of color photographic material wherein at least one silver halide emulsion layer containing a developablesilver salt is color developed to yield a dye image, the developed silver and the residual silver halide being removed, there is provided the step of developing the photographic material with a color developing solution in the presence of an image-forming color coupler and a formazan compound of the following general formula I:

v a I where R, and R are each selected from hydrogen atoms or solubilizing groups and R is a hydrogen atom or an aryl, alkyl, aralkyl or a -CN group or a solubilizing group selected from COOH, -CH SO;,H or CH COOH, at least one of R ,'R or R being a solubilizing group, the two phenyl groups optionally carrying further substituents.

Examples of suitable solubilizing groups are SO H, CH SO H. -COOH, CH COOH, -O-CH COOH.

The formazan compound of the above defined formula whether present initially in the photographic material or present in the color developing solution is able to couple with oxidized color developing agent to form a colorless product. It

is believed that the colorless product is the derived tetrazolium salt.

The formazans used in the process of the present invention are colored yellow to red in alkaline solution but due to their great solubility and lack of affinity for gelatin very little if any remains in the photographic material after the washing step which follows color development. However if any does remain in the photographic material it is oxidized to a colorless compound in the bleaching bath, as a bleaching step is present as hereinafter described in all types of color processing, in order to remove the developed silver from the material.

The process of the present invention is particularly of use in the processing of a multilayer color material of the type in which there are three gelatino silver halide emulsion layers, selectively sensitive to blue, green and red regions of the spectrum, each layer containing a color coupler substantive thereto, which yields on color development a dye image complementary in color to the color sensitivity of the layer containing it. The color material may be of the type which yields a direct color image on development or may be of the type which is used to produce reversal color images. It is also applicable in the reversal processing of color photographic material wherein the image-forming color couplers are not present initially but are present in each color developing solutron.

It is preferred that the compounds of the above formula are present in the color developing solution or solutions but they may be present initially in the photographic material and in this case preferably in each silver halide containing layer.

When the compounds of the above formula are present in the color developing solution they are preferably present at a concentration of 0.5 to 5 g./liter. In the case of substantivecolor-coupler material the exact concentration depends on the desired effect and on the silver halide/color coupler coating weight.

The examples set out later herein relate to photographic material of the reversal type. The usual processing sequence for exposed material of this type comprises the following steps which are well known in the art:

1. Black and white development.

2. Hardening bath.

3. Washing bath.

4. Reexposure.

5. Color development.

6. Wash and/or acid stop bath.

7. Bleach.

8. Washing bath.

9. Fixing bath.

l0. Washing bath.

1 l. Conditioning treatment.

The only factor which is likely to vary greatly when processing different materials is the composition of the color development bath. In Example 1 which relates to a reversal material containing substantive color couplers a color development bath of the following composition was used:

Trisodium phosphate g.

Hydroxylamine sulphate 2.4 g.

Anhydrous sodium sulphite 4.0 5.

Potassium bromide l.0 g. N-ethyl-N-hydroxyethyl p-phenylene diamine sulphate 5.7 g.

Water to 1 liter The following preparation is inserted to show how a particular compound of formula I may be prepared.

PREPARATION OF 1-3 :-sulphophenyl-3-methyl-5- phenylformazan Q-i iQ C H; Compound I 200 parts of metanilic acid are suspended in 1,200 parts of water at 30 C. and dissolved by the addition. of 40 parts of sodium hydroxide. 70 parts of sodium nitrite are added and the resulting solution diazotized by adding dropwise to a solution of 400 parts of water and 472 parts of concentrated hydrochloric acid 36 Tw keeping the temperature below 5 C.

The diazotized suspension is added to a stirred solution of 140' parts of acetaldehyde phenyl hydrazone in 2,000 parts of pyridine keeping the temperature below 5 C. After stirring for 30 minutes the deep red solution is acidified to Congo Red paper with concentrated hydrochloric acid keeping the temperature below 'l0 C. A further 472 parts of concentrated hydrochloric acid are added to precipitate the product fully.: After collection by filtration the formazan dye is washed with 2N hydrochloric acid and then acetone. After drying at 50 C. 268 parts of a bluish grey powder are obtained which dissolves readily in dilute sodium carbonate to give a yellow solution.

The following Examples which make use of compound I will serve to illustrate the invention.

EXAMPLE 1.

, periment to the color developer. The density of the processed film to blue, green and red filters is measured and plotted against log exposure to obtain the three familiar characteristic curves. Since the maximum density of the strip obtained by standard processing procedure is too high for comparison the densities of each strip are compared at the shoulder" of the curve at the same exposure level. The following results are obtained EXAMPLE 2.

Trisodium phosphate 80 g.

,Hydroxylamine sulphate 2.4 g.

Anhydrous sodium sulphite 4.0 g.

.Potassium bromide 4.0 g. iS-Diethylamino-Z-aminotoluene ihydrochloride 2.0 g.

: l-Phenyl-J-coumariIylamido-S-pyrazolone 2.0 g.

2 liter Water to The strips were washed, acid stopped, bleached, washed, fixed, washed and conditioned in the normal manner. Strips ;were also processed with the addition of 2 g. of Compound I l-3'-sulphophenyl-3-methyl-5-formazan) to 1 liter of the color developing solution. Strips were also processed with the addition of 2 g. of citrazinic acid to 1 liter of the color Zdeveloping solution. A further set of strips was processed in the same color developing solutions which had been allowed ;to stand for 4 days. The following results were obtained on measurement of the maximum density of the strips to a green filter.

Maximum Density to Green Filter Initial After 4 days .Standard color developer, 40 gnn additions 3.7 3.5 I IAddition of 2g./l. formazan 1.5 L5

3A of 2g./l. citrazinic iacid 2.7 2.3

It will be seen from these figures that the formazan, like citrazinic acid, is effective in reducing the density and contras of the color developed layers. This higher silver coating weight material processed with either the formazan or citrazinic acid] gives a better grainiriess in general than a conventionall i coated and processed material. However since the effect on the green filter density is greater for the formazan than citrazinic acid when the effect on the blue and red densities are equal, upward adjustment of silver coating weights to give: a material balanced for processing with the formazan will give. a better graininess than a material balanced for processing with citrazinic acid.

Part of the measured blue filter density is due to blue ab-. sorption of the magenta dye. lf analytical density measure ment are carried out it showsthat the effect on the yellow dye; density is less for the formazan than for the citrazinic acid. This is beneficial since whereas the yellow dye of the blue sen sitive layer does not contribute much to visual graininess, use of the formazan allows the silver coating weight of this layer to be cut down, with a beneficial effect on sharpness and speed of the underlying layers. I

Density Density Density to B to G. to R 3 filter filter filter Standard color developer, 1 no additions 2.69 2.83 2.95 Addition of 0.63 gJl. formazan 2.53 2.56 2.82

|.2s g./l. formazan 2.41 2.27 2.39

1.75 g./l. formazan 2.32 2.08 2.12

5 g./l. citrazinic acid 2.32 2.32 2.12 l

v The measurements show the efi'ective decrease in maximum fdensity and hence contrast of the magenta image. The meazsurement of the density after 4 days storage of developer shows the stability of such a solution. Examination of the graininess at equal densities shows an improvement for the 'formazan and citrazinic acid processed strips.

EXAMPLE 3 'of the processed strips to a green filter and are given in the following Table I. Compounds ll to V have the general formula in the preparation of Compound I acetaldehydephenylhydrazone is replaced by an equivalent amount of acetaldehydephenylhydrazone-4-carboxylic acid to give compound, VI. in similar fashion, by the reaction of diazotised orthanilici acid, sulphanilic acid, 4-aminobenzoic acid and 4- chloroaniline-2-sulphonic acid with acetaldehydephenylhydrazone-4-carboxylic acid there are obtained the formazan compounds Vll, Vlll, lX and X respectively. These are addedi to developer as described in Example 2 but at the rate of l g./liter. The comparative effect of the addition can be ex-i pressed by the percentage reduction in the maximum density? of the processed strips to a green filter and are given in the following Table Il. Compounds 1V to X have the general formulai llli i l RD" -N HNOOOH l i s R5 R1 7 i C 3s 41H: III

TABLE ll Compound R, R R, Percentage reduction in Maximum Density l V! H 50,14 H 2i 45 Vll SO,H H H 18 i Vlll H H SO H l3 [X H H COOH 16 X SO=H H Cl 16 Citrazinic Acid l3 i lclaim as my invention I i y 1. In a process of color development of color photographic material wherein at least one silver halide emulsion layer containing adevelopable silver salt is color developed to yield a dye image, the developed photographic material is washedand the developed silver and the residual silver halide are removed, the steps of developing the photographic material with a color developing solution in the presence of an imageforming color coupler and a soluble formazan compound of the formula:

where R and R are each hydrogen or a solubilizing group selected from --SO H, CH SO H, COOH, CH COOl-l or --OCH COOH and R is a hydrogen atom or an aryl, alkyl, aralkyl or a CN group or a solubilizing group selected from COOH, CH SO H or CH COOH, at least one of R,, R or R being a solubilizinggroup as defined, or a corresponding iormazan compoun in which at least one of the where R, and R are each hydrogen or a solubilizing group selected from SO H, CH SO H, COOH, CH COOH or -O--CH COOl-l and R is a hydrogen atom or an aryl, alkyl, aralkyl or a CN group or a solubilizing group selected from COOH, -CH SO H or CH COOH, at least one of R,, R or R being a solubilizing group as defined, or a corresponding formazan compounds in which at least one of the indicated phenyl groups carries a further substituent which does not reduce the solubility of the compound.

3. A color developing solution according to claim 2 wherein the formazan compound is present at a concentration of 0.5 to 5 g. per liter. 

2. A color developing solution which comprises a color-developing agent and a soluble formazan compound of the formula:
 3. A color developing solution according to claim 2 wherein the formazan compound is present at a concentration of 0.5 to 5 g. per liter. 